Valine (Val) alone or in combination with isoleucine (Ile) improves the growth under severe protein restriction; however, the underlying mechanisms remain unknown. In this study, we assessed whether Val/Ile-induced growth in protein-restricted pigs is associated with changes in gut development, hepatic insulin-like growth factor 1 (IGF-1) production, and blood metabolomics. Forty piglets were assigned to five dietary groups: positive control (PC) with standard protein content; low protein (LP) with very low protein content; and LP supplemented with Val (LPV), Ile (LPI), and Val and Ile (LPVI). LPVI reversed the negative effects of VLP diets on growth and gut morphology. Both LPV and LPVI restored the reduced transcript of IGF-1 while decreasing the transcript of insulin-like growth factor binding protein 1 (IGFBP1) in the liver. LPV and LPVI recovered the reduced plasma Val, glycine, and leucine concentrations, which were positively correlated with improved gut morphology and the hepatic IGF-1 gene expression and negatively correlated with hepatic IGFBP1 mRNA abundance. In conclusion, supplementation with a combination of Val and Ile into the VLP diets restored the decreased growth performance of pigs fed with these diets likely through improved gut development, hepatic IGF-1 expression and bioavailability, and plasma metabolomics profile.
Little is known whether a combination Ile and added Val improves the growth of pigs offered very low protein (VLP) diets through changes in nutrients digestibility and gut microbiota. The objective of this study was to investigate the effect of a mixture of Val above and Ile at NRC levels on growth, nutrient digestibility and gut microbiota in pigs fed with VLP diets. Forty, weaned piglets were assigned to: positive control: normal-protein-diet; negative control (NC): VLP diet supplemented with first four limiting amino acids; VA: NC with Val above NRC; IL: NC with Ile at NRC level; VAIL: NC with Val above and Ile at NRC levels. While both VAIL and VA groups completely recovered the inhibitory effects of VLP diets on feed intake, only VAIL partially recovered the negative effects of VLP diets on growth performance. VAIL and VA increased the thermal radiation and decreased the digestibility of nitrogen. NC increased the relative abundance of Pasteurellaceae and Enterobacteriaceae in the colon. VAIL had a higher abundance of colonic Actinobacteria, Enterococcus, and Brevibacillus and the colon content of VA was more enriched with Mogibacterium. Overall, VAIL partially improved the growth performance which is likely linked with alterations in gut microbiota composition.
Very low protein (VLP) diets decrease the nitrogen excretion from pigs, but these diets depress the performance even when the first four limiting amino acids (FFL; i.e. Lys, Met, Thr and Trp) are added. Supplementation of Val above and Ile at NRC (2012) levels has shown promising effects on performance of pigs fed with VLP diets. The objective of this study was to investigate the effect of a mixture of Val above and Ile at NRC levels on growth and gut microbiota in pigs fed with VLP diets. Three-week-old, weaned piglets (n = 40) were assigned to: 1) positive control (PC): normal protein diet; 2) negative control (NC): VLP diet with FFL at NRC levels; 3) VA: NC with Val above NRC; 4) IL: NC with Ile at NRC level; 5) VAIL: NC with Val above and Ile at NRC levels. Following 5 weeks of data collection, colon contents were collected. The data were analyzed by GLM procedure followed a t-test with Benjamini-Hochberg correction (SPSS). Pigs fed with NC had decreased average daily gain (ADG) and average daily feed intake (ADFI), compared with PC (P< 0.05). VAIL had less ADG than PC, but that tended to have greater ADG than NC (P< 0.1). Further, VAIL had a similar ADFI as PC (P>0.05) and tended to have greater ADFI than NC (P< 0.1). Compared with PC and NC, pigs fed with VAIL had a higher thermal radiation (P< 0.05). Relative to PC, the colon content of NC was enriched in Pasteurellaceae while those fed with VAIL had a greater abundance of Bacillus, Brevibacillus, Enterococcus, Actinobacteria, which might contribute to improved performance of pigs fed with VAIL diets. Overall, supplementation of a mixture of Val greater than NRC and Ile at NRC into the VLP diets partially improved the performance, which is likely linked with alterations in gut microbiota composition.
Increased feed cost, post-weaning diarrhea, and nitrogen excretion are challenging the modern swine industry. Very low-protein (LP) diets (>4% units reduced protein) may reduce feed cost, diarrhea and nitrogen excretion; however, these diets impair growth performance of pigs despite supplementation of limiting amino acids (i.e., lysine, threonine, methionine and tryptophan). The objective of this study was to investigate the effect of valine, isoleucine and combination of both supplemented to VLP diet on growth, thermal radiation, and gut development in young pigs. Forty three-week-old weaned barrows were weighed (6.75 ± 0.14 kg) and randomly assigned to five groups (8 pigs/group) including: 1) standard diet or positive control (PC), 2) LP diet, 3) LP + valine (LPV), 4) LP + isoleucine (LPI) and 5) LP + both valine and isoleucine (LPVI) for five weeks. Daily feed intake and weekly growth characteristics were measured and weekly thermal images were captured. All pigs were euthanized at week 5 and tissue samples collected. All data were analyzed with univariate GLM followed by Tukey’s post-hoc test (SPSS®). Compared to PC, final body weight, average daily gain, average daily protein intake and gain:feed ratio were reduced in LP group, but feeding pigs with LPVI partially or completely recovered these parameters. Pigs fed with LPVI had higher thermal radiation than those fed with PC, LP, and LPI on days 28 and 35 of study and had a greater the area under the curve for thermal radiation than LP and LPI. Duodenal villus width and crypt depth, and ileal villus height were decreased in LP relative to PC, but LPVI either partially or fully recovered these measurements. In conclusion, supplementing a combination of valine and isoleucine recovered the negative effects of very low-protein diets on growth performance and gut development, but increased the thermal radiation in weaned pigs.
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